Human Interleukin-17 (IL-17) is a cytokine of 30 kDa produced by activated memory T cells. Unlike other IL-17 ligands, IL-17A (also simply referred to in this proposal as IL-17) is unique in that it has a distinct and specific receptor, which differs from other receptors. IL-17 receptor is ubiquitously expressed. Hence, IL-17 has large variety of target tissues. IL-17 stimulates expression and secretion of IL-1 B, IL-6, IL-8, GM-CSF, G-CSF, ICAMs and PGE2. It regulates hematopoietic cell proliferation, the immune system and fine-tunes hematopoiesis. Clinically, it has significance in various human diseases including cancer, arthritis, lymphomas, leukemia and pro-inflammatory diseases. The mechanisms of how IL-17 elicits its biologic functions are not well understood and are the focus of this investigation. Our laboratory has demonstrated that IL-17 triggers activation of multiple signaling pathways including the Jak/STAT and Ras/MAPK pathways. Recently, we have observed that specific PKC isoforms are induced during IL-17 stimulation of leukemia cells. Further, we have detected that IL-17 induces PI-3Kinase (PI-3K) and PDK-mediated phosphorylation of Akt on Ser473 and Thr308 and Akt activation. However, the significance of both the PKC and PI-3K/Akt activation in the mechanisms of the biologic functions of IL-17 remains unknown. This will be the main objective of this proposal. Based on our preliminary results, we hypothesize that both the PKC and PI-3k/Akt-mediated mechansims play critical roles in the IL-17R signaling leading to specific biologic response to IL-17. The specific aims of this proposal are (1) determination of the significance of activation of specific PKC isoforms by IL-17, (2) determination of the significance of activation of the PI-3K/Akt pathway in the mechanisms of IL-17, and (3) identification of possible cross talk between the PKC and the PI-3K/Akt signaling pathways. To address these aims, we strategize to employ multiple approaches involving applications of pharmacological inhibitors, anti-sense gene knockout, dominant negative (DN) gene knockout and protein overexpression in cells untreated or treated with IL-17. We propose to use a host of molecular, cellular, and biochemical techniques including ELISA, protein kinase assays, Flow Cytometry, PCR, Real Time PCR, RT-PCR, Cytokine Affimetrix microarrays, cell cycle analysis, Mass Spec, apoptotic assays, Western/Northern blot hybridization and tissue culture to achieve our goals.